1. Field of the Invention
The present invention relates to a brake for a vehicle. More particularly, the present invention relates to a disk brake for a vehicle having a power transmission device that presses a friction pad against a disk by using a worm gear.
2. Description of the Related Art
In general, a disk brake for a vehicle generates braking force by pressing friction pads against both sides of a disk, which rotates together with a wheel. Such a disk brake for a vehicle includes friction pads that make contact with both sides of a disk rotating together with a vehicle wheel to generate braking force, a wedge member, which is provided at one side thereof with the friction pad and moves toward the disk by means of a driving motor that generates driving force, and a guide member which guides the wedge member such that the wedge member can move toward the disk being rotated. The wedge member is inserted between the disk and the guide member so that great braking force can be obtained even if low power is applied during the braking operation.
In addition, the disk brake for the vehicle further comprises a power transmission device, which moves toward the disk by means of the driving motor to allow the wedge member to move toward the disk being rotated.
In order to allow the power transmission device to move toward the disk, a male screw is formed around a rotating shaft of the driving motor and a shaft hole having a female screw is formed at an inner peripheral portion of the power transmission device. Thus, the power transmission device can move back and forth relative to the disk according to the rotational direction of the rotating shaft of the driving motor. Such a conventional disk brake requires a brake booster, which reduces deviation through deceleration and increases braking force when the braking operation is performed by using rotational force of the driving motor. The brake booster may include a pair of wedge members having inclined surfaces facing each other.
However, if the wedge members are used as the brake booster, although great braking force can be obtained through the self-energization, there is great variation in the braking force, so that the braking operation cannot be easily controlled. In addition, vibration and shock, which are generated when the friction pads make contact with the disk, may be transferred to the driving motor through the wedge members. Further, if repulsive force is applied to the rotating shaft of the driving motor, the driving motor may malfunction.